The present invention relates generally to an apparatus for dispensing a substantially uniform layer of an aggregate material onto a roadway surface. More particularly, the present invention relates to an aggregate spreader having a hopper, attached to a motor vehicle, which receives an aggregate material from an aggregate source and dispenses predetermined quantities of the aggregate material in a layer having a substantially uniform thickness.
A widely used, economical method for building and/or repairing roadways is commonly known as "chip sealing." The chip sealing process entails the deposition of a layer of asphalt or oil onto the roadway bed, after which an aggregate mix is deposited onto the asphalt or oil layer and the aggregate is rolled to seat the aggregate into the asphalt or oil layer. Contractors will typically over deposit the aggregate to assure adequate binding of the aggregate into the asphalt to form the overlayer for the roadway. Such practices, however, invariably result in loose aggregate on the roadway being thrown up by vehicles traveling on the roadway which causes property damage to following vehicles, traffic accidents and possibly injury. Moreover, the practices of over depositing of aggregate are wasteful and non-economical.
To achieve a uniform spread of aggregate material it is necessary to achieve uniform deposition of the aggregate material across the spread width and along the entire length of the spread path. Most of the conventional spreaders have focused only on the problem of deposition uniformity across the spread width and have left the problem of uniformity along the length of the spread path to the vagaries of manual control.
A variety of such material spreading and/or dispensing systems have been devised by those skilled in the art. Illustrative of such conventional material spreading and/or dispensing systems are the following:
A. U.S. Pat. No 1,200,274 entitled "HOISTING BUCKET" to Thomas on Feb. 3, 1916, discloses a hoisting bucket having two bottom doors which are actuated by a trip lever to unload the contents of the hoisting bucket.
B. U.S. Pat. No. 1,880,287 entitled "ASPHALT MIXER" issued to Sifton on Oct. 4, 1932, discloses an asphalt mixer having a bottom oscillating panel which feeds asphalt from the lower opening of the hopper onto a conveyor. The oscillating plate is under control of a rotary piston arrangement which serves to laterally displace the bottom plate.
C. U.S. Pat. No. 3,054,160, entitled "SHUTTLE CARS," issued to Le Tourneau on Sept. 18, 1962, discloses a self-propelled load hauling and self-dumping shuttle car such as that used in a mine. This patent discloses a pivoting gate which opens and closes through a pinion gear, and is illustrative of a pivoting gate arrangement.
D. U.S. Pat. No. 2,663,439, entitled "TELESCOPIC DUMPING TRUCK", issued to Phelps on Dec. 22, 1953, discloses a telescoping dump truck which has an expansible/retractable enclosure for carrying as well as dispensing. The telescoping dump truck consists of a series of hydraulically driven plates, each of which are slidably engaged with an interior surface of an outlying plate. This patent provides an example of an hydraulically actuated expansible enclosure.
E. U.S. Pat. No. 4,023,719, entitled "HOPPER CLOSING AND EMPTYING DEVICE," issued to Noyon on May 17, 1977, discloses a pivoting hopper gate wherein the gate is located in the vicinity of a third corner of a triangular linkage and an actuating lever is provided for opening of the gate. The door of the gate swings free of the bottom of the hopper to allow the material to be dispensed.
F. U.S. Pat. No. 4,484,852, entitled "HOPPER BOTTOM UNIT," issued to Anderson on Nov. 27, 1984, discloses a vibrating hopper bottom unit which facilitates discharge of a material from the bottom of the hopper. The unit consists mainly of a flexible membrane which is oscillated by a vibrator mounted on a beam attached to the vibrating membrane. The vibrator 160 includes a motor which oscillates the vibration beam attached to the membrane.
G. U.S. Pat. No. 4,697,951, entitled "MATERIAL SPREADER SYSTEM" issued to Allen on October 6, 1987, discloses a spreader which stores a supply of a material for dispensing a layer of the material as the spreader is transported along a defined path. With particular reference to FIGS. 6A and 6B of this patent, a gate is provided which consists of clamp shell doors. A linkage which actuates clamp shell doors is provided. The linkage attached to the gates may include an actuator arm which is, in turn, attached to a pneumatic cylinder. A series of pneumatic air vibrators are coupled to the hopper which contains the material to be dispensed. The air vibrators commence operation when the actuator is operated to open the gate. The vibrations produced by the air vibrators cause the hopper surfaces to vibrate, thereby causing the material within the hopper to be uniformly metered through the gate.
H. The Flaherty SPK-H Chip Spreader manufactured by Seaman Company of Milwaukee, Wis. provides a fixed width spreading hopper which has an interior spread roll and agitator bar within the hopper. Cutoff gates are provided to allow for variable spread widths. Radial-type gates are remotely controlled from the operator's deck and open in one-sixteenth increments from 0 to 4.5 inches. The gate openings are established and set manually. The gates are forward mounted and aggregate passing through the hopper is laterally distributed by the interior spread roll and agitator bar.
I. E. D. Entyre & Co. of Oregon, Ill. manufactures mechanical and hydrostatic self-propelled chip spreaders, which both employ a fixed width hopper. The hopper is fitted with a hydraulically driven agitator and spread roll, which are actuated by gate opening. The spread gates are forward mounted, and have individual shut-off controls. Gate openings are established and set manually via a dial on the instrument panel.
J. E. D. Entyre & Co. also manufactures a variable width spreading hopper, consisting of two independent spread hoppers which are independently operated and fed with aggregate. Each spread hopper has a spread roller which turn in opposite directions. The remaining operational features are identical to the Entyre spreader noted in item "I" above.
Those skilled in the art will appreciate that the abovedescribed material spreaders and dispensers fail to provide adequate uniformity of material spreading and lack automated controls which facilitate uniformity of material spreading under various roadway conditions.